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Quynh N.T.,Gyeongsang National University | Hikima J.-I.,University of Miyazaki | Kim Y.-R.,Gyeongsang National University | Fagutao F.F.,Gyeongsang National University | And 3 more authors.
Fish and Shellfish Immunology | Year: 2015

DDX41, a receptor belonging to the DExD family, functions as a DNA sensor in the mammalian cytoplasm and mediates the antiviral response in host cells. Here, the olive flounder DDX41 was found to have 2267-bp long and encodes a putative protein of 614 amino acid residues. The olive flounder DDX41 mRNA was presented in all tested tissues, and was distinctly expressed in fish naturally infected with LCDV. High expression levels were observed in the heart, liver, kidney and stomach. Furthermore, the olive flounder DDX41 mRNA expression increased significantly in adherent (monocyte-like) cells following stimulation with a DNA virus. Reporter assays showed that the transcriptional activity of the IFN-I promoter was enhanced in DDX41-overexpressing HINAE cells treated with C-di-GMP (dinucleotides). Overexpression of DDX41 also induced the antiviral and inflammatory cytokine gene expression through cytoplasmic C-di-GMP treatment. These results suggest that DDX41 functions as a cytosolic DNA sensor that is capable of inducing antiviral activity and inflammatory responses in the olive flounder. © 2015 Elsevier Ltd.

Yona D.,Pukyong National University | Park M.O.,Pukyong National University | Oh S.J.,Pukyong National University | Shin W.C.,BluGen Korea
Ocean Science Journal | Year: 2014

Recently, studies on the influences of physico-chemical properties of water masses on the distribution of Synechococcus have been conducted. In addition, it is known that different types of Synechococcus can be identified based on its phycoerythrin (PE) chromophores, which are phycourobilin (PUB) and phycoerythrobilin (PEB). This study observed the abundance of Synechococcus and its phycoerythrin chromophores based on the excitation ratio of PUB and PEB, and also examined the major environmental factors which influence the distribution of Synechococcus in the East Sea during autumn 2011 and spring 2012. Surface distribution showed that the abundance of Synechococcus in autumn was higher than that in spring (6.5 ± 4.7 × 103 cells ml-1 in autumn and 1.2 ± 0.9 × 103 cells ml-1 in spring) when water temperature was warmer and nutrient level was higher. Vertical distribution of Synechococcus abundance showed sub-surface maxima for both seasons between 10–30 m depth. Surface distribution of the PUBEX:PEBEX ratio was found in a slightly similar range between autumn and spring (0.83–1.45 in autumn and 0.82–1.34 in spring). Vertical distribution of the PUBEX:PEBEX ratio ranged between 0.77–1.57 and 0.82–1.42 in autumn and spring, respectively. This study is one of the very few studies that examined the PUBEX:PEBEX ratio in the natural samples and found three different types of Synechococcus based on its PUBEX:PEBEX ratio: high PUBEX:PEBEX ratios (> 1) in warm surface layers and in the deeper layers for both seasons; low PUBEX:PEBEX ratios (< 1) in the surface layer in autumn; and a few PUB-lacking Synechococcus. The distribution of the PUBEX:PEBEX ratio was clearly associated with temperature and salinity in which a low PUBEX:PEBEX ratio coincided with colder and less saline water, and vice versa. © 2014, Korea Ocean Research & Development Institute (KORDI) and the Korean Society of Oceanography (KSO) and Springer Science+Business Media Dordrecht.

Kim S.W.,Gyeongsang National University | Jang H.B.,Gyeongsang National University | Lee J.S.,Gyeongsang National University | Im S.P.,Gyeongsang National University | And 5 more authors.
Journal of Microbiological Methods | Year: 2015

The olive flounder (Paralichthys olivaceus) is a cultivated marine species that is economically important in Korea and Japan. Several bacterial pathogens have caused severe mortalities in farmed olive flounder, especially Streptococcus parauberis. We collected 145 S. parauberis isolates from diseased olive flounders from 2003 to 2008 in Jeju Island, South Korea and characterized them by Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI TOF MS) and by serology. The serological analysis divided the isolates into serotype I (62.1%) and serotype II (36.6%) and the proteome analysis divided the isolates into cluster 1 (43.4%) and cluster 2 (56.6%). All cluster 1 isolates had serotype I, but cluster 2 consisted of serotype I (32.9%), serotype II (64.6%), and others (2.5%). Further detailed analysis of the mass spectra led to identification of several specific m/z peaks that enabled discrimination between cluster 1 and 2 and between serotype I and II within cluster 2. Our results suggest that MALDI TOF MS analysis has potential as an alternative method for the rapid and reliable identification of the fish pathogen S. parauberis. © 2015 Elsevier B.V..

Kim S.-H.,Norwegian University of Life Sciences | Kim M.,BluGen Korea | Choi G.-E.,BluGen Korea | Lee J.H.,Fish Breeding Center | And 3 more authors.
Vaccine | Year: 2016

Viral hemorrhagic septicemia virus (VHSV) is the causative agent of viral hemorrhagic septicemia in fish, a disease that affects a number of teleost fish species including olive flounder (Paralichthys olivaceus). In this study, we assessed the safety and efficacy of two recombinant attenuated VHSV strains, termed A4G-G5A and δNV, with the purpose to select the most suitable vaccine strain. The virus strains were passaged in two commercially available cell lines, EPC and RTG-2, and the strains were also tested for residual virulence in zebrafish (Danio rerio). The A4G-G5A strain showed an attenuated growth profile in both the EPC and RTG-2 cell lines compared to wild-type (WT) VHSV (JF-09, genotype IVa), whereas the growth profile of δNV was comparable to the WT strains in RTG-2 cells in contrast to EPC cells. Moreover, δNV had higher residual virulence compared to A4G-G5A and was highly pathogenic to zebrafish. The A4G-G5A strain was chosen as vaccine candidate and tested for efficacy in in vivo fish studies in the target species, olive flounder, using an immersion vaccine scheme. Groups of fish were immunized with 102.5, 103.5, 104.5, and 105.5 TCID50/ml of A4G-G5A giving 5-13.3 cumulative percent mortality (CPM) post immunization. Immunization was followed by a challenge experiment using VHSV-WT. The relative percent survival (RPS) in immunized groups ranged from 81.6% to 100%, correlating with vaccination dose. This study demonstrates that while strain A4G-G5A has retained some residual virulence it confers high level of protection in immunized olive flounder. © 2016 Elsevier Ltd.

Park S.B.,Mississippi College | Nho S.W.,Mississippi College | Jang H.B.,Gyeongsang National University | Cha I.S.,Gyeongsang National University | And 3 more authors.
Aquaculture | Year: 2016

Streptococcus iniae and S. parauberis types I and II are major bacterial pathogens affecting the olive flounder, Paralichthys olivaceus. With the introduction of formalin-killed vaccine for S. iniae, recent epidemiological studies have indicated that S. parauberis infections are becoming increasingly severe and frequent in the olive flounder farming industry. Here, the formalin-killed bacterins were used to develop a three-valent vaccine against three streptococcal infections, and its efficacy was assessed in laboratory- and field-challenge trials. In the laboratory-challenge test, it obtained 75%, 75% and 90% relative percent survival (RPS) values in vaccinated olive flounders challenged with S. iniae, S. parauberis type I, and S. parauberis type II, respectively. For the field-challenge trial, the three-valent vaccine was administered to over 100,000 olive flounders, which were compared to non-injected control fish. An RPS of 74% was observed when S. parauberis infection naturally occurred at 11 fish farms. Serum antibody measurements using olive flounder immunoglobulin-specific antibodies indicated that immunized fish had significantly higher serum antibody levels than control fish up to 6 months post-vaccination. These results demonstrate that the three-valent vaccine using formalin-killed bacterins could effectively protect olive flounders against three major streptococcal infections. Statement of relevance: The olive flounder, P. olivaceus, is an economically important fish species in Northeast Asia and the most valuable fish species in South Korea, corresponding to 56.5% of the total mariculture production in 2010 (Baeck et al., 2006). However, streptococcal infections often break out among farmed olive flounders subjected to certain conditions (e.g., high stocking density, poor water quality and high water temperature), leading to mass mortality and severe economic losses (Baeck et al., 2006; Cho et al., 2008) Antibiotic treatments are usually recommended to address such outbreaks, but the prevalence of multi-drug-resistant bacteria means that antibiotic compounds are not always able to eradicate the infections (Creeper and Buller, 2006). The Gram-positive bacteria, Streptococcus iniae and S. parauberis, cause streptococcosis and have severe effects on aquaculture of the olive flounder, barramundi, channel catfish, European sea bass, rainbow trout, striped bass, tilapia, turbot and yellow tail (Gudmundsdóttir and Björnsdóttir, 2007; Han et al., 2011). In the olive flounder, fish infected with S. iniae usually show severe pathological changes, such as darkening, exophthalmia, rectal hernia, abdominal distension, ascites and congestion of intestinal organs, whereas fish infected with S. parauberis rarely exhibited any remarkable pathological finding except for darkening of the skin (Kim et al., 2006).Some vaccines have been reported to prevent S. iniae infection, showing high relative percent survival (RPS) among olive flounders in laboratory trials; such vaccines are now commercially available (Cheng et al., 2010a). However, recent epidemiological studies have suggested that S. parauberis infection has increased and become more severe and frequent as much as infections of S. iniae, which was previously considered the major bacterial pathogen among olive flounder (Park et al., 2012; Park, 2009; Perera et al., 1998). S. parauberis can be divided into two serotypes (types I and II) based on serological testing of a distinctive capsular polysaccharide layer (Bromage and Owens, 2002; Plant and Lapatra, 2011). Since the two serotypes possess specific antigenic characteristics, a vaccine should be able to address both types in order to effectively prevent S. parauberis infection. The present study was undertaken to develop a three-valent vaccine against both serotypes of S. parauberis plus S. iniae using formalin-killed vaccine preparation method. The efficacy of this vaccine against the major streptococcal infections of olive flounder was calculated as RPS and conducted in both laboratory trials and large-scale field trial. This vaccine will be highly useful and more advantageous since the use of this does not require several antibiotics which means safer food production and more sustainable environment. © 2016 Elsevier B.V.

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